1. Field of the Invention
The invention relates generally to measuring optical characteristics of plasmas and more particularly to measuring opacity and emissivity coefficients of a dense plasma.
2. Description of the Prior Art
There is a growing class of technical applications of plasmas that requires an accurate determination of the emissivity and absoption of the plasma utilized. Examples of these applications include: impoving the radiation environment of laser-driven nuclear fusion reactions, developing X-ray lasers, testing the effectness of laser weapons, and processing of materials.
Spectroscopic methods are utilized to measure the emissivity and absorption of plasmas. The emissivity coefficient of the plasma is a measure of the rate at which photons are emitted by the plasma. Similarly, the absorption coefficient is a measure of the rate at which photons are absorbed by the plasma. A major drawback of the accuracy of existing measurement techniques is the need to average over plasma temperature and density gradients. Computational techniques have been developed to average over these gradients but they are generally uneconomical and inaccurate.
Additionally, for a dense plasma these measurements are complicated by the self absorption of the plasma. The emissivity and absorption coefficients in the plasma may not be independently measured in a nonuniform plasma if the absorption is significant as in a dense or optically thick plasma.